Preformed Protein Sources in Steer Finishing Rations

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Abstract
Eighty yearling steers averaging 290 kg were fed in a 146-day trial to study the performance of steers fed corn silage with protein supplements of varying solubility (corn, soybean, fish and linseed protein). The effects of protein supplements on plasma amino acids, plasma urea-nitrogen, ruminal ammonia and ruminal volatile fatty acids were also studied. Average daily gains were lowest (P< .05) for .steers fed corn as the only protein source. Carcass quality grade, marbling score, ribeye area, fat thickness and dressing percentage were not altered (P< .05) by the source of supplemental protein. Plasma glycine, valine, leucine, lysine, arginine and total amino acids were highest (P< .05) on day 69 for steers fed fishmeal. Total plasma amino acids were higher (P< .01) for steers fed fishmeal than for those receiving soybean meal. Plasma urea-nitrogen was lowest (P< .05) for steers fed corn alone. Ruminal volatile fatty acids were not different (P< .05) on day 69 or day 140. Copyright © 1974. American Society of Animal Science . Copyright 1974 by American Society of Animal Science.